Otolith shape analysis supports three cryptic species in the Stellifer punctatissimus complex (Acanthuriformes: Sciaenidae)

Sciaenidae species (croakers and drums) are known for specializations in their sensory apparatus, such as otoliths and lateral line. Within this family, some Stelliferinae members remain taxonomically unresolved due to their cryptic aspects and low phenotypic disparities. Stellifer punctatissimus comprises a species complex putatively formed by three species on morphological grounds, but molecular data have indicated only two evolutionary lineages. Herein, we tested the hypothesis that this complex is composed of Stellifer gomezi (GM), S. menezesi (MN), and S. punctatissimus (PC), using the otolith shape and morphology to differentiate them. Seventy-seven sagittal otoliths (GM = 30, MN = 30, PC = 17) were photographed to outline the otolith contour by Elliptical Fourier descriptors. Ten otoliths for each group were used to detect shape variation in the sulcus acusticus through semilandmarks. Differences in otolith shape contour were recorded among the species by PERMANOVA (Pseudo-F = 4.02, df = 2, p < 0.001) and corroborated by the Linear Discriminant Analysis, which demonstrated three partially segregated groups with satisfactory re-classification rates. A larger sulcus acusticus (GM and MN), rounded projection (PC), and distinct rectangularity pattern were also recorded. Our results support the morphological hypothesis and thus contribute to narrowing the taxonomic gaps in Sciaenidae.

Keywords:
Croakers; Cryptic species; Otolith morphology; Speciation; Taxonomy